Apparatus for wide-ranging, high-accuracy fluid (p,ρ,T) measurements based on a compact two-sinker densimeter

McLinden, Mark O.; Lösch-Will, Cornelia

doi:10.1016/j.jct.2006.09.012

Cited by 95 publications

(140 citation statements)

References 26 publications

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“…The two-sinker densimeter recently put into operation at NIST [7] has sinkers made of titanium and tantalum with nominal masses of 60 g each and volumes V Ti = 13.35 cm 3 and V Ta = 3.61 cm 3 . It also incorporates two calibration weights that are placed onto the balance pan by small robotic arms.…”

Section: Force Transmission Error Analysismentioning

confidence: 99%

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Force Transmission Errors in Magnetic Suspension Densimeters

2007

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Techniques to determine and compensate for the force transmission error (FTE), including the magnetic effects of the fluid being measured, in magnetic suspension densimeters are presented. For a two-sinker densimeter, the forces on the balance are expressed for each of the weighings comprising a density determination (i.e., the two sinkers plus balance calibration and tare weights). This yields a system of four equations, which are solved for the fluid density, a balance calibration factor, a coupling factor (related to the FTE), and a quantity related to the balance tare. For a single-sinker densimeter, an in situ weighing of the sinker in vacuum compensates for the FTE of the apparatus itself. A determination of the fluid-specific effect requires measurements with two different sinkers-analogous to the two-sinker analysis, but with the measurements spread out over time. The apparatus part of the FTE is generally less than ±20 ppm. Measurements on propane, helium, neon, nitrogen, argon, toluene, and air are analyzed for the fluid-specific effect; this effect is correlated with the magnetic susceptibility of the fluid together with an apparatus constant. With this analysis, the force transmission "error" becomes an effect that can be accounted for rather than a significant source of uncertainty in density measurements carried out with magnetic suspension densimeters.

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Section: Force Transmission Error Analysismentioning

confidence: 99%

“…Most fluids are weakly diamagnetic, and φ displays a behavior similar to that seen with propane. Helium, neon, nitrogen, argon, and toluene have also been measured in the NIST two-sinker densimeter; these data are reported elsewhere [7,10,12]. The slope (∂φ/∂ρ) for these fluids is given in Table I and plotted as a function of χ s in Fig.…”

Section: Figmentioning

confidence: 99%

Force Transmission Errors in Magnetic Suspension Densimeters

2007

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“…The two-sinker densimeter used in this work is described in detail by McLinden and Lösch-Will [1] and McLinden and Splett [2], and this general type of instrument is described by Wagner and Kleinrahm [3]. In the present densimeter, two sinkers of nearly the same mass, surface area, and surface material, but very different volumes, are weighed separately with a high-precision balance while immersed in a fluid of unknown density.…”

Section: Densimetermentioning

confidence: 99%

Certification Report for SRM 2214: Density of Iso-octane for Extended Ranges of Temperature and Pressure

McLinden¹,

Splett²

2016

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______________________________________________________________________________________________________This publication is available free of charge from: https://doi.org/10.6028/NIST.SP. This report of analysis documents procedures used to obtain certified values and associated uncertainties of the density of iso-octane SRM 2214 over an extended range of temperatures and pressures. This SRM is certified over the temperature range -50˚C to 160˚C and pressure range of 0.1 MPa to 30 MPa; an interpolation model is provided to calculate the density within these ranges. This SRM has a density of 691.853 kg⋅m -3 at t = 20˚C and p = 0.1 MPa. The certification measurements were carried out in a two-sinker magnetic-suspension densimeter. The SRM material is commercial, high-purity iso-octane (2,2,4-trimethylpentane, CAS 540-84-1). Measurements were made on both degassed material and material saturated with nitrogen, and an estimated correction surface (valid over the range -50˚C ≤ t ≤ 100˚C and 0.1 MPa ≤ p ≤ 20 MPa) gives the density difference between the nitrogen-saturated and degassed materials. A thorough analysis of the uncertainties is presented; this includes effects resulting from the experimental density determination, possible degradation of the sample due to time and exposure to high temperatures, dissolved air, uncertainties in the empirical density model, and the sample-tosample variations in the SRM vials. Also considered is the effect of uncertainties in the user's temperature and pressure measurements. This SRM is intended for the calibration of industrial densimeters.

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“…We accounted for frequency shifts and/or energy losses induced by bulk effects, the presence of a thermal boundary layer (including the temperaturejump effect with the thermal accommodation coefficient h = 1, and the propagation of a thermal wave into the shell), the coupling of gas and the breathing mode of shell motion, and the presence of a vent hole machined through the resonator wall. To calculate the corrections, the density of helium was obtained iteratively from the virial equation of state at fourth order, with values of the density virial coefficients from [7,15]. The thermal conductivity and viscosity of helium at zero-density were obtained from [7].…”

Section: Acoustic Measurements In Heliummentioning

confidence: 99%

“…We calculated theoretical values of the speed of sound v theory as a function of pressure using the virial expansion, with values for the second acoustic virial coefficient from the ab initio results in [7] and values of the third virial coefficient, and their temperature derivatives from recent pρT measurements [15]. The three different frames in Fig.…”

Section: Acoustic Measurements In Heliummentioning

confidence: 99%

Progress Towards an Acoustic Measurement of the Molar Gas Constant at INRIM

et al. 2007

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Progress in developing an experiment for the determination of the molar gas constant R and the Boltzmann constant k at INRIM is reported. The experiment involves simultaneous measurements of the acoustic and microwave resonance frequencies of a stainless steel spherical resonator for which its hemispheres were deliberately misaligned. For the present work, these frequencies were measured in helium near 273.16 K, in the pressure range from 100 to 800 kPa. From microwave data, the radius of the resonator was determined as a function of pressure with an estimated uncertainty of 6.0 ppm. Using acoustic data and the microwave determination of the resonator radius, the speed of sound in helium was deduced, and these values were compared with those predicted by recent accurate ab initio calculations. Over most of the pressure range, the present values agreed with the ab initio values within the uncertainty of the measurements (standard uncertainty of approximately 7.0 ppm). Many suggestions for reducing the uncertainty are provided.

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Apparatus for wide-ranging, high-accuracy fluid (p,ρ,T) measurements based on a compact two-sinker densimeter

Cited by 95 publications

References 26 publications

Force Transmission Errors in Magnetic Suspension Densimeters

Force Transmission Errors in Magnetic Suspension Densimeters

Certification Report for SRM 2214: Density of Iso-octane for Extended Ranges of Temperature and Pressure

Progress Towards an Acoustic Measurement of the Molar Gas Constant at INRIM

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